1. Field of the Invention
This invention relates to a bearing assembly mounting structure, and, in particular, to a structure for mounting a linear motion rolling contact bearing assembly to a supporting structure, such as a machine frame.
2. Description of the Prior Art
A bearing assembly is fixedly mounted on a supporting structure when used. For example, in the case of a linear motion rolling contact bearing assembly including a guide rail extending straight over a length, a slider member which moves along the guide rail and a plurality of rolling members interposed between the guide rail and the slider member to provide a smooth relative motion between the guide rail and the slider member, both of the guide rail and the slider member must be fixedly attached to respective supporting members, such as a machine frame and an object to be moved.
As shown in FIG. 5, a guide rail 1 is typically formed by bending a steel plate so as to have a U-shaped cross section so that it has a bottom wall and a pair of side walls extending upward from opposite sides of the bottom wall. Each of the side walls of the guide rail 1 is provided with a guide groove at its outer surface so as to receive a plurality of balls 5 as rolling members. The outermost distance defined by the outermost points of the balls 5 on both sides of the guide rail 1 as shown in FIG. 5 is designated by P.sub.2, and this distance P.sub.2 must be maintained within a predetermined accuracy. However, since the guide rail 1 is typically formed from a steel plate by bending, even if the distance P.sub.2 is set within a predetermined tolerance after manufacture, it is likely that the bottom wall of the guide rail 1 is not straight, but it is warped outwardly as shown in FIG. 5. In such a case, when the guide rail 1 is fixedly mounted on a supporting member 2, such as a machine frame, by means of a bolt 3, it is highly likely that the distance P.sub.2 would change beyond a predetermined tolerance as bolt 3 is tightened. Another such example is shown in FIG. 8, in which, the U-shaped guide rail 1 is warped inwardly prior to tightening of the bolt 3.
On the other hand, even if the guide rail 1 has an almost perfect U-shape after manufacture as shown in FIG. 7, when the bolt 3 is tightened, there is produced an elastic deformation by the amount, thereby defining a deflection angle .theta. shown in FIG. 6. With such a deflection angle .theta., there is also produced an error in the distance P corresponding to the change in expanse between the outermost points of the balls 5 on both sides of the guide rail 5. The presence of such an error in the distance P is not desirable because this could severely affect the performance of the bearing assembly as a whole. For example, there could be produced an increase in rolling contact resistance or a significant play for the balls interposed between the guide rail 1 and the slider member.